The porpoise population in the Dutch part of the North Sea has grown considerably in the last thirty years. More than seven times as many animals were spotted in 2019 as in 1991. Nevertheless, the number of porpoises close to the coast has decreased slightly in recent years. This is shown Monday from figures from Statistics Netherlands, which collaborated with Wageningen Marine Research (WMR) for this.
Harbor porpoises were a common species in the North Sea before the 1940s. After that, the number decreased sharply, but an upward trend can be observed again from 1991.
According to Statistics Netherlands, the increase in the number of porpoises in the North Sea is related to the change in the living environment of the mammals. In recent years, this has partially shifted from the northern North Sea to the Dutch part of the North Sea.
The numbers of porpoises observed varied greatly within a year from 26,000 (in October-November 2010) to 86,000 (March 2011). The porpoises are no longer on the Red List of endangered mammals since November 3, 2020.
In addition to the increase in population, the number of strandings of dead porpoises along the coast also increased. In the early 1990s, no more than a few dozen animals per year were stranded, but by 2012 this had increased to more than 980. The most common causes of death are drowning in fishing gear, infections, starvation and collisions with ship propellers.
For the data, WMR used various monitoring systems, including aerial analyzes and annual counts from Rijkswaterstaat.